When trouble occurs at a node or in a link inside the high speed packet communication network, a detour path detouring the node or the link at which the trouble occurs must be set. Furthermore, an identifier(s) of a packet directional path(s) must be set for each link of this detour path.
In the conventional communication network, a network control center monitors the state of transmission lines in the whole network, and when trouble is informed thereto from a node, the control center searches for a path detouring the node or link at which the trouble occurs, and switches the line. In such a centralized control system, there is a problem that it takes a long time to switch the path and a heavy burden is imposed on the network control-center.
Therefore, in the high speed packet communication network, a system which automatically searches for a detour path by flooding from a node detecting the trouble has been developed. In this flooding: the node which detects the trouble sends a detour path search message for indicating the node itself as a terminal node of the detour path, and a start node of the detour path, to links in all directions connected thereto; and
each node which receives the detour path search message, when the node is not the start node, inserts information on the node to indicate that the node is a node the detour path search message passed through, and sends the detour path search message, to links connected thereto in all directions if the node itself is not the start node. If the node which receives the detour path search message is the start node, it sends a detour path setting message which is composed so that the detour path setting message traces back through the nodes through which the detour path search message has passed, to the terminal node, where information on the nodes to be passed through is contained in the detour path search message. In this way, the detour path is determined.
For the detour path determined in the manner described above, however, the identifier(s) of the packet directional path(s) in each link must be set. This identifier(s) of the packet directional path(s) must be made to correspond to the identifier(s) of the packet directional path(s) which has been set for an outgoing link of the start node in the original packet directional path(s).